Recording MIDI data, as described above, has a huge advantage over recording with a microphone: The results are almost infinitely editable. For example, you can delete wrong notes or drag them onto the right ones. If you played a section too loud, you can lighten it up after the fact. You can change the tempo or key of the music, making it faster, slower, higher, or lower, without distortion. If you discover a more appropriate instrument sound for a certain part, you can reassign the whole part.
In fact, GarageBand even lets you edit the invisible data generated by the foot pedal and control wheels.
The key to all of this freedom is the nature of the recordings you make with a MIDI keyboard: GarageBand stores your performance as a series of scheduled note triggers. When you play back your piece, GarageBand plays its own built-in synthesizer in real time. It’s not playing back a sound recording.
The doorway to all of this editing magic is the Track Editor, shown in Figure 26-9.
You can open this window in any of several ways:
Double-click a green region in the timeline. This is the best way to open the Track Editor, because it appears prescrolled to the notes in the region you clicked.
Click the scissors icon () beneath the track headers. The Track Editor opens to the beginning of the first region on the track.
Choose Control → Show Editor, ...